Manufacture of tubes



June 6, 1933 c. W. LITTLER MANUFACTURE OF TUBES Filed Nov.

INVENTOR Patented June 6, 1933 UNITED STATES PATENT ol-FICE CARL `w.I.I:1"I'LIIR`,or PITTSBURGH, PENNSYLVANIA, AssIGNoR To ,IoNns a LAUGIILIN STEEL` CORPORATION, oF PITTSBURGH, PENNSYLVANIA, A coRPoRATIoN or I'RNN- sYLvANIA MANIIFACTURE oF TUBES Thisinifention relates broadlyito the Inanufacture of tubes, and more particularly to the manufacture of seamless tubes. It relates `still more "particularly to the manufacture ofseamless tubesby the push bench process. The term tube is used herein as a word of definition and notof limitation, and is not to be construed as denoting only that class' of articles commercially known as tubes.

In the `push bench process of manufacturingseamless tubes a heatedmetal billet is pierced in a press to form a blank open at one end and closed at the opposite end, commonly referred to as'a bottle; and the bottle thus formed is placed over the nose/of a mandrel and pushed through a seriesof dies which thinand elongate thebottle over the mandrel to form a tube blank closed at its forward end.` The tube blank is then stripped from the mandrel and its i ends sawed "olf `to produce a finished tube. In certain variations of the push benehprocess theblank, `after havingits ends sawed ofi', may undergo various finishing operations, such as expanding in a Stiefel or plug mill, polishing and straightening. However. a blank of proper dimensions Inay, upon having its ends cut ofhand upon straightening, if necessary, serve as a finished tube, as the surfaces imparted by the mandreland push bench `dies are suitable for the `inished product. i

One of the. principal problems in the push bench process is that incident to the high cost ofmandrels. Push `bench mandrels are made. of icostly alloy steel. The cost of a single mandrel may run well up into the thousands of dollars. The mandrels may be feet or more in length and weigh several tons apiece. The mandrels should be perfectly straight and must have great compressive strength to `withstand the tremendous pressures to which they are subjected in the push bench. i i i i In order to reduce so far as possible the high cost of mandrels` and to make them of aweight which will permit handling, I propose that theybe formed hollow. Even hol` low mandrels are tremendously heavy; for

example, a hollow mandrel for forming 16` inch tubes fifty feet inlen th weighs well over twenty thousand poun s, but neverthefortunately, however, the use of a hollow mandrel will aggravate another operating problem. In operation the mandrels arenot only subjected to tremendous pressures, but also to high temperatures, particularly near the i forward end orznlose thereof, and, although hollow mandrels may be made rigid enough, generally speaking, their continual reuse Awilleventually result in reduction in diameter at at least a `portion thereof.` The same will be true, although to a lesser extent, with solid mandrels, which, if reused a sufficientnumber of times, will undergo a reduction in size. Y

, It has heretofore been customary, particularly with push `bench apparatus so designed that the tube blank formed `on the mandrel is intended to be of finished size as to internal diameter, to discard the mandrel upon apprec-iable reduction in size thereof. The life of a mandrel has therefore been limited in accordance with its ability to withstand such reduction. Following such practiceit would be necessary to quickly discard hollow mandrels which, except for decrease in diameter, would be otherwise satisfactory `for further use. When the external diameter of the mandrel has been relied upon to internally size the tube blank, any appreciable reduction in the external diameter of the `mandrel has rendered it `unlit for `performing this function. It has been` customary to withdraw such aimandrel from serviceand recondition it before further use, thus entailing additional cost and4 necessitatingthe substitution of another mandrel.

I propose to do away with the waste here-` tofore occasioned by withdrawing from less a great saving in weight is effected. Un-

service mandrels whosesize has been appre ciably reducedby continuing such mandrels in service, even after substantial reductionin size, so as to form tube blanks whose internal diameters are smaller and smaller and then inishing such blanks into tubes of desired :finished dimensions. For example, I may purposely place in service a mandrel which is oversize, that is to say, whose external diameter is substantially greater than would be the external diameter of a mandrel designed in accordance with usual practice for the production of tubes of a desired internal diameter, and continue to use such mandrel so long as its external diameter has not become reduced below the desired internal diameter of the finished tubes. The tube blanks formed on such mandrel may be subjected, after having their ends sawed ofi", and, if desired, after being reheated, to the action of reducing rolls which reduce them to the size desired for the finished tubes;

I provide a process for the manufacture of tubes by the use of a push bench, comprising utilizing` a mandrel for the formation of tube blanks in a -push bench until the diameter of at least a portion of such mandrel has been materially reduced by the pressures exerted thereon in the blank forming operation, thereby resulting in the formation of tube blanks the respective diameters of which are smaller and smaller, and linishing each of such blanks into a tube of predetermined slze.

Other objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawing I have shown diagrammatically apparatus suitable for carrying out the invention, wherein Figure l is a diagrammatic plan view of a portion of a plant layout for the manufacture of Vtubes by the push bench process; and

Figure 2 is a longitudinal cross-sectional view through a mandrel adapted for use in a push bench for the manufacture of seamless tubes.

As above stated, a billet of suitable size is first heated in a'furnace and then placed in a press where it is pierced throughout the major portion of its length to form the bottle. The internal diameter of such bottle is preferably such that it may conveniently be placed over the end of a mandrel of desired size. The mandrel, carrying the bottle over its forward end, is moved axially through the push bench wherein the walls of the bottle are thinned and elongated between the mandrel and the dies to form the tube blank.

Referring now more particularly to the drawing, the push bench is illustrated diagrammatically in Figure 1 by reference numeral 2, the respective dies being designated at 3. Such dies are axially aligned and are coaxial with the path of movement of the mandrel. The dies are of decreasing size in the direction of advance of the mandrel, that is to say, from left to right, viewing Figure 1, so as to effect a step-by-step reduction in the size of the bottle as it is formed into the elongated tube blank. v

One suitable form of mandrel is shown in Figure 2. Such mandrel is of the hollow type and comprises a tubular body portion 4 necked in at one end as at 5. At such end the mandrel body carries a tail 6 which has a hub 7 of such size as to snugly fit within the reduced extremity of the mandrel body. A key 8 maintains the tail in place with respect to the body 4:. At its opposite end the body carries a nose 9 having a reduced eX- tension l0 adapted to enter `the extremity of the body and to be keyed thereto by a key 11. The` nose 9 is preferably made of high heat resistant alloy steel of great strength to withstand the tremendous pressures and high temperatures encountered in pushing the bottle through the dies of the push bench.

The internal diameter of the tube blank formed on the mandrel will be substantially the same as the external diameter of the mandrel inasmuch as the metal of the blank is pressed tightly against the surface of the mandrel by the dies during formation. Therefore, if, for example, it is desired to produce a blank whose internal diameter is inches, it would be customary to provide a mandrel whose external diameter is 6 inches, or possibly very slightly less. Such mandrel can be used a limited number of times in the production of blanks having an internal diameter of 6 inches. Upon continued use the mandrels, at certain portions at least, become reduced in size. The mandrel body 4 just behind the nose extension l0 becomes, as it were, swaged inwardly due to the high pressure at the forward end of the mandrel. The mandrel body 4 may be formed of steel less highly resistant than the steel of which the nose 9 is made, and, furthermore, the extreme forward portion of the body is reinforced by the extension 10 of the nose. This reduction in the mandrel body will during subsequent use be extended rearwardly, and the nose itself, being subjected to the highest pressures, will likewise feel the effect of some reduction in size.

In installations in which the mandrel is relied upon to size the blanks, the mandrel would, in accordance with usual practice, be replaced and reconditioned upon any substantial reduction in size. However, I propose to lengthen the life of the mandrel before it becomes necessary to recondition it by continuing it in service, even after substan tial reduction in size, to produce tubes whose internal diameters are smaller and smaller. In fact, I prefer when initially placing the mandrel in service to have its diameter ap preciably oversize to allow for substantial reduction while still producing blanks whose internal diameters are not less than the desired internal diameter of the finished tubes. The mandrel as initially introduced into service may be from 2 to 5 per cent or more oversize as to external diameter. This allows for substantial reduction in size of the mandrel before its diameter becomes less than the internal diameter desired for the finished tubes.

When the tube blanks formed on the mandrel are of greater internal diameter than that desired for the blanks are reduced to the desired dimensions. The blanks formed after the mandrel has undergone substantial reduction in size will not require to be reduced to as great an eX- tent as those formed earlier in the life `of the mandrel. As the external diameter of the mandrel approaches the desired internal diameter of the finished tubes the reduction necessary in the blanks becomes less and less so that the last few blanks formed on a mandrel before it is removed from service may require no subsequent reduction.

In order to insure `that the blanks will be reduced to the proper finished external and internal dimensions, the cross-sectional area of the blanks is controlled, as the mandrel undergoes reduction in size, by reducing the size of the last one or two dies in the push bench. The object of this provision is to form the blanks of such a cross-sectional area that upon the subsequent reduction thereof to the desired finished internal diameter the desired finished external diameter will be obtained. In other words, the reduction may be effected between rolls which impart to the finished tube the proper finished external diameter,` and by reason of the control of the cross-sectionalarea of the blank the `internal diameter will automatically come to size. Thecross-sectional area of the blanks as fornied `on the mandrel will preferably be somewhat greaterthan the desired cross-sectional area' of the finished tubes, as when the blanks are passed through the reducing rolls themetal will ordinarily undergo some longtudinal flow, thereby reducing the crosssectional area as well as the internal and external dimensions.

Referring now again to Figure 1 of the drawing, the blank with the mandrel within itis moved from the push bench upon rollers 12 through a reeler or cross-rolling mill 13,

which serves to loosen the blank on ithe mandrel to` facilitate stripping. This is more lully set forth in Peters Patent No. 1.720,- 345. The reeler may be dispensed with, if desired, particularly when short relatively thick blanks are formed which may more readily be stripped from the mandrel than longer thinner blanks.

The mandrel with the blank thereon is then advanced upon rollers 14 whence it moves across skids 15 onto rollers 16 in alignment with a mandrel stripper 17, which may be of any well known type and which, therefore, is illustrated ,only diagrammatically. The blank is stripped from the, mandrel by the `stripper 17, whereupon the mandrel is returned upon rollers 18 for reuse, previous to which it may, if desired, be re-heated and finished tubes, such From the rollers 24 the blank is passed through reducinglrolls contained within a housing designated diagrammatically at 29, and which rolls and housing may be of conventional type. There may be two or more stands of rolls whose axes are disposed at dif'-v ferent angles, the rolls being adapted to re` duce theoversized blank to the dimensions desired for the finished tube,` as above explained. i i -i i f Ifthe blank, after having its ends sawed off, is of finished dimensions and doesnot require to be passed through the reducing rolls, `it maybe advanced upon the'rollers 27 to a straightening machine (not shown), if necessary."

Although I prefer to introduce the mandrel into operation oversize with respect to the size ofthe tubes to be formed, and t0 reduce the `blanks formed on the mandrel during continued use to tubes of commonfinished size, I may instead finish the smaller blanks formed after the mandrelyhas under,- gone substantial reductionin `size into tubes of smaller size than those formed from blanks 'produced earlier in the lifeof the mandrel. In eitherevent, the life and usefulness of the mandrel is greatly increased and the cost of the operation greatly reduced. Due tothe provision of the reducing rolls in combination with the continued use of the mandrel, even after substantial reduction in size, the tubes do not suffer in quality and the finished tubes produced from blanks formed at various stages of the life of the mandrel will be commercially identical. i

The term material reduction and like terms as used in the claims in reference to alteration of the size of the mandrelcomprehend such a reduction in mandrel sizeas wouldresult, in ordinary mill practice,yin discontinuance of useof the mandrel forthe formation of tubes of the size forwhich it was designed.` i y While I have shown and described certain present preferred embodiments-of the inven tion, it is to be distinctly understood that the same is by no means limited thereto, but may be otherwise lvariously embodied and praeticed within the scope of the following claims.

I claim:

1. A process for the manufacture of tubes by the use of a pushbench, comprising providing a mandrel whose diameter is initially materially greater than the desired internal diameter of the finished tubes, forming tube blanks on such mandrel in a push bench, thereby eventually reducing the diameter of at least a port-ion of the mandrel, 19 reducing the tube blanks toV desired finished size, and continuing the use of such mandrel even after material reduction in its size, whereby the useful life of the mandrel is materially increased. 1 2. A process for the manufacture of tubes by the use of a push bench, comprising providing a mandrel whose diameter is initially materially greater than the desired internal diameter of the finished tubes, forming tube blanks on such mandrel in a push bench, thereby eventually materially reducing the diameter of at least a portion of the mandrel, continuing to form tube blanks on such mandrel even after such material reduction in diameter, and providing die means in the push bench adapted for cooperation with the mandrel in the formation of each such tube blank to form such blank of a predetermined approximate cross-sectional area. 3. A process for the manufacture of tubes by the use of a push bench, comprising providing a mandrel Whose diameter is initially materially greater than the desired internal diameter of the finished tubes, forming tube blanks on such mandrel in a push bench, thereby eventually materially reducing tlie diameter of at least a portion of the mandrel, Continuing` to form tube blanks on such mandrel even after such material reduction in diameter, providing die means in the push bench adapted for cooperation with the mandrel in the, formation of each such tube blank to form such blank of a predetermined approximate cross-sectional area, and reducing the tube blanks to desired finished size. 4. A process for the manufacture of tubes by the use of a push bench, comprising providing a mandrel Whose diameter is initially materially greater than the internal diameters of at least some finished tubes the blanks for which are formed thereon, forming tubey blanks on such mandrel in a push bench, thereby eventually reducing the di ameter of at least a portion of the mandrel, reducing at least some of the tube blanks t desired finished size, and continuing the use of such mandrel even after material reduction in its size, whereby the useful life of the mandrel is materially increased. i

In testimony whereof I have hereunto set CARL W. LITTLER. 

